Construction for reinforcing a center pillar in a subway tunnel, a column of an overpass or a parking structure, a column of a building immediately after a disaster, or the like, takes place under a condition with heavily restricted working space and working time.
For example, when reinforcing a center pillar in a subway tunnel, the reinforcement must be implemented in a short period of time at night, outside of operational business hours. Specifically, considering that current flows in the subway tracks for 30 minutes after the current supplied to the tracks is stopped, there are only several daily working hours at night when the trains are stopped, i.e., a construction time of about 3 hours from 1 AM to 4 AM.
In addition, working space is extremely limited, as the space between a center pillar and a train is narrow. Since the working space that can be secured in a subway tunnel is narrow in this manner, heavy machinery or large equipment cannot be used. The same time and spatial limitations are imposed when reinforcing a column of an overpass or a parking structure, or a column of a building site where a disaster has occurred.
Methods for reinforcing a column of a building structure by surrounding the perimeter of the column with a reinforcing material in order to enhance the earthquake resistance of the column have been proposed heretofore.
For example, Japanese Laid-Open Publication No. 9-177334 (Patent Literature 1) discloses a construction method for reinforcing a concrete column. The method of reinforcement disclosed in Patent Literature 1 is a method comprising: disposing a plurality of steel plates 40 so as to surround a concrete column 1; overlaying end sections of adjacent steel plates 40 and coupling the end sections with a bolt/nut 41; and filling a space 42 between the concrete column 1 and the steel plate 40 with grout as shown in FIG. 12.
Further, Japanese Laid-Open Publication No. 2005-23745 (Patent Literature 2) also discloses a construction method for reinforcing a concrete column. The method of reinforcement disclosed in Patent Literature 2 is a method comprising: disposing steel plates 45 with a cross-section formed in an L-shape on the four corners of a concrete column 1 so as to surround the concrete column 1; binding the steel plates 45 by wrapping a belt-like fiber sheet 46 on the outer perimeter of the steel plates 45; and filling a space 42 between the four steel plates 45 and the concrete column 1 with grout as shown in FIG. 13.
However, the curing period required for grout filled into the space between the concrete column and steel plates to solidify is long in these construction methods for reinforcement. Thus, the methods of reinforcement disclosed in these Patent Literatures cannot be employed as a method of reinforcement under a condition where reinforcement work must be implemented in a short period of time as in the above-described case of reinforcing a center pillar of a subway tunnel. In addition, since these methods of reinforcement require the use of injection equipment for injecting grout into the space between a pillar and a steel plate in a narrow working space, work at a construction site would be extremely difficult.
As a method for reinforcing a column subjected to reinforcement (e.g., concrete column) without using grout, the inventors investigated a method comprising disposing a plurality of steel plates in a transverse direction so as to surround the perimeter of a column subjected to reinforcement and wrapping a belt-like fiber sheet thereon while applying an adhesive to the outer circumferential surface of the steel plates. Since this method does not use grout, work can be carried out expeditiously, in addition to the level of earthquake resistance being equivalent in comparison to a case of using grout (e.g., see Non-Patent Literature 1: this document studies the level of earthquake resistance capability of a reinforcing steel plate using mortar, which is also grout). However, a fair amount of curing time is required for the applied adhesive to sufficiently function as an adhesive. For this reason, it would be difficult to quickly and efficiently complete reinforcement work within a limited working time. Even when the amount of adhesive applied was increased to further enhance the adhesiveness, the adhesive dripped down until the adhesive suitably cured, and time and effort were required to remove the adhesive which dripped down onto the ground or floor.